Ring-opening metathesis polymerization (ROMP) is a popular method for the preparation of a variety of functional polymers and is one of the most prevalent technologies that has emerged from the development of transition metal-based olefin metathesis catalysts. Applications in areas such as drug delivery, biomedical engineering, photovoltaics, and production of structural materials have each benefited from developments in ROMP methods. In general, ROMP is used to achieve living polymerizations, to provide polymers of narrow dispersity, to enable control over end group functionality, and to incorporate a broad range of functional groups into polymer scaffolds and network materials.
Traditional ROMP initiators include transition metal complexes, such as Ru, W, or Mo-alkylidene complexes, along with a number of ill-defined species containing various mixtures of metal salts. Examples of Ru-, Mo-, and W-based alkylidene initiators are shown in Scheme 1 below.

It is believed that each of these initiators proceeds through the same general mechanism involving a metallacyclobutane intermediate as shown in Scheme 2, below, where M is a metal and R is a substituent.
Despite the positive attributes that traditional transition metal catalysts can provide to a ROMP process, a significant disadvantage common to transition metal-catalyzed ROMP is that metal-based byproducts can be difficult to remove from the polymeric materials. This can lead to complications with biological studies, conductivity measurements, or optical properties. Moreover, downstream reactivity of residual metallic species can also be problematic. At a minimum, the potential for metal contaminants often warrants quantitation by advanced techniques, such as inductively-coupled plasma mass spectrometry. Indeed, these issues have motivated a number of protocols for removing metal-based components, which, even when successful, add additional processing steps for material production.
Thus, there is presently a need for polymerization using organic initiators, for cross-linking reactions that do not require metal catalysts, and for reaction products that do not have trapped metals. The present disclosure seeks to fulfill these needs and provides further related advantages.